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Serena Williams suffers pulmonary embolism

Serena Williams at Wimbledon in July 2010. The tennis champion is now undergoing… (Julian Finney/Getty Images )

A representative for Serena Williams told reporters Wednesday that the tennis star was receiving treatment for a pulmonary embolism she suffered last week. Here's what that means:

FOR THE RECORD: An earlier version of this report incorrectly referred to the American College of Cardiology as the American College of Cardiologists.

A pulmonary embolism is a blood clot, usually originating in a vein in the upper thigh, that breaks loose and travels to a lung. Classically, a person develops a pulmonary embolism when he or she has risk factors for the problem — including pregnancy, use of oral contraceptives, clotting problems and obesity — and then remains sedentary for a period of time, allowing blood to stagnate in the leg and form a clot.

People who take long airplane trips and car rides are at risk for pulmonary embolism. So are people who suffer an injury that keeps a leg immobilized. Williams cut tendons in her right foot when she stepped on some broken glass in July. It is possible that clotting around that injury site contributed to her pulmonary embolism, said cardiologist Dr. Ralph Brindis, president of the American College of Cardiology.

Another possibility is that Williams’ clot originated in her arm at the subclavian vein, which in muscular athletes can get compressed below the collarbone and first rib. But Brindis said he’d be “very surprised” if that was an issue in this case.

Typically, doctors treat pulmonary embolism by administering anticoagulant drugs such as Warfarin or Coumadin to prevent additional clotting. Williams may be on the medications for several months, doctors said.

In some cases, large emboli are also initially treated with clot dissolving agents. Brindis said that such agents can cause bleeding in other parts of the body, which may be the explanation for treatment of a hematoma — an area of bleeding — mentioned in the statement by Williams’ representative.

Dr. Mark Adelman, chief of vascular and endovascular surgery at NYU Langone medical center, said that Williams’ lungs should heal completely. The length of time to heal the original clot, whether it was in her leg or in her arm, could vary depending on its size and other factors.

Adelman estimated that for anywhere from six to 12 weeks her doctors won’t want her to play tennis at all. After that, Williams might be able to play at a high level, but because the anticoagulants will put her at additional risk of bruises and bleeding, she’ll want to avoid getting hit hard during play.